The Vitavac patented system is able to preserve goods for 1 year and beyond by allowing products to breath and degas. Almost all food goods are smell proof inside the Vacs , however some products like freshly roasted coffee and MEDICAL HERBS may degas, leaking there odor. Our 2 way valve allows gas build up to slowly escape – without letting oxygen in. This is one of the main reasons it can preserve goods for long periods of time.